Tensioning apparatus for tenuous material



2 Sheets-Sheet l m MN W III g o I II I I INVENTOR. ZEONARD A. KARBER BYAfibfifliy Aug 7, 1962 L. A. KARBER TENSIONING APPARATUS FOR TENUOUSMATERIAL Filed April 6, 1959 I I I I I I I I I 3,048,346 TENSIONINGAPPARATUS FOR TENUOUS MATERIAL Leonard A. Karber, Sharon, Pa., assignorto Herr Equipment Corporation Filed Apr. 6, 1959, Ser. No. 804,339 8Claims. (Cl. 242-755) The present invention relates to tensioningapparatus, more particularly to apparatus for maintaining apredeter-mined tension on longitudinally moving tenuous material, andthe principal object of the invention is to provide new and improvedapparatus of the character described.

Apparatus for tensioning longitudinally moving tenuous material has longbeen used in the manufacture, handling and processing of metal strip andlike materials. Heretofore, however, none of this apparatus has beensulficiently sensitive for certain operations. For example, one of suchoperations requires that a length of metal strip be fed horizontallythrough an oven, supported only at its ends, so that such strip portionforms a catenary. Sufiicient tension must be maintained on the strip toprevent excessive catenary depth; however, since in some instances thestrip may be as thin as a thousandth of an inch and since its tensilestrength may be lower than normal because of oven heat, the maximumtension to which the strip can be subjected without exceeding its yieldpoint is apt to be quite limited. The net result of the foregoingcircumstances is to require that the strip be accurately tensionedwithin very close limits.

Prior art tensioning apparatus, while suitable for less critical uses,has been unsuitable under conditions above described when a relativelyheavy tension must be maintained within extremely close limits. Incontrast, the present invention may apply any desired tension on movingstrip, within the design limits of the device of course, which tensionwill be maintained With a variance of less than one pound. This is trueeven though the applied tension may amount to hundreds of pounds. Otheradvantages will readily become apparent from a study of the followingdescription and from the drawings appended hereto.

In the drawings accompanying this specification and forming a part ofthis application there is shown, for purpose of illustration, anembodiment which the invention may assume, and in these drawings:

FIGURE 1 is a side elevational view of a preferred embodiment of theinvention shown in combination with a portion of a continuous stripprocessing line,

FIGURE 2 is an enlarged side elevational view of the improved tensioningapparatus seen in- FIGURE 1,

FIGURE 3 isan end elevational view of the apparatus seen in FIGURE 2,

FIGURE 4 is a top plan view thereof, and

FIGURES 5 and 6 are diagrammatic views illustrating an operatingprinciples of the apparatus.

With reference to FIGURE 1, there is shown tensioning apparatus 10 beingused for tensioning strip material S as it passes in the direction ofthe arrows through an elongated oven or like device 11. At the left, orentrance end of the oven, there is positioned a pair of pinch rolls 12between which the strip passes and which tightly grip the latter.Although not shown, these pinch rolls are adapted to be rotated by anysuitable means to pass the strip to the oven at a predetermined rate.

Apparatus 10, forming the subject matter of the pres- 3,048,346 PatentedAug. 7, 1962 ent application for Letters Patent, is adapted to withdrawthe strip from the oven at substantially the same rate at which thepinch rolls 12 feed the strip thereinto and to pass the strip tosubsequent strip handling apparatus of any desirable type which is,however, not illustrated since it neither forms a part of the presentinvention nor is it necessary for an understanding thereof. As willappear, appear, apparatus 10 not only functions to draw the strip fromthe oven but also functions to place the strip portion within the ovenunder the desired tension. Briefly, the reason for tensioning the stripportion within the oven is as follows:

In many instances, of which the present case is an example, it isessential that the strip be freely suspended within the oven; that is,the strip cannot be supported interiorly of the oven by underlyingrollers or the like but must be supported entirely by the strip portionsprojecting from respective oven ends. Obviously, since the strip extendshorizontally through the oven, the weight of the strip causes it to sag.It is to prevent excessive sagging of the strip which necessitates thetensioning thereof.

It is to be understood that when relatively heavy strip is beinghandled, the tensioning thereof does not present a serious problem andmany of the prior art tension devices may be satisfactorily employed.Indeed, when the processing line with which the present apparatus isassociated is employed With strip more than about ten thousandths of aninch thick, the present device need not be used for tensioning at allsince conventional tensioning devices at other parts of the processingline will function satisfactorily for tensioning the strip portionwithin the oven. This results because of the fact that when suchrelatively heavy strip is being processed, a tensioning forceconsiderably in excess of that necessary to properly tension the stripmay be readily exerted thereon without harmful results. When, however,strip having a thickness of, perhaps, one thousandth of an inch is beingprocessed, the amount of force necessary to properly tension the stripmay be very close to the maximum force which can be exerted on thestrip, especially in its weakened condition as a result of its elevatedtemperature within the oven, without stretching, rupturing or otherwisedamaging the strip. It is to maintain the above described delicatebalance of tensioning force upon relatively thin strip which is aprincipal object of the present tensioning apparatus.

Still refer-ring to FIGURE 1 but as also seen in FIG- URE 2, apparatus10 presently comprises a pair of rolls 13 and 14 rotatably supported inspaced-apart relation by respective roll stands 15 and 16. It is to henoted that rolls 13, 14 are herein shown to be of the same diameter andthat their axes lie in a plane which is generally parallel tothe desiredpath of travel of the strip through the oven (it being understood, ofcourse, that the strip will not assume within the oven the straight lineillustrated but will sag downwardly therefrom at its central portions)so that the upper peripheries of such rolls will be tangent to a planewhich is parallel to such desired path of strip travel.

As illustrated, the strip emerges from the oven and passes over therolls 13, 14, being deflected to a loop formation between such rolls aswill hereinafter be more particularly described, and over a roll 17disposed beneath roll 14 and rotatably carried by the roll stand 16.From the roll 17, the strip passes to any desired strip handlingdevices. Although not shown, an additional roll may be provided to forcethe strip closely against the periphery of either of the rolls 14, 17 toinsure against slippage between these rolls and the strip. For the samepurpose, rolls 14, 17 may have their working faces coated with asuitable non-slip material such as rubber or the like.

As previously mentioned, apparatus is adapted to Withdraw from the oven,strip fed thereinto by the pinch rolls 12. Accordingly, means 18 isprovided (see FIG- URE 3) for driving the rolls 14, 17. Such means maybe of any suitable type capable of speed regulation for a purpose toappear. In the present embodiment, roll 13 carried by stand is notdriven but is merely an idler roll.

Still referring to FIGURES l and 2, the strip S is adapted to bedeflected into a loop formation intermediate the rolls 13, 14, asheretofore disclosed, by means of an idler roll 19 which is bodilyshiftable vertically (in the position of parts shown) to increase anddecrease the size of the strip loop. (Note that roll 19 is of a diameterto pass between the rolls 13, 14 so that it may be shifted from the fullline position seen in FIG- URE 2 to the phantom line position indicatedat B when its use is not required to tension the strip.)

It is an important feature of the present invention that roll 19 ismovable in a rectilinear path which is perpendicular to a plane tangentto the upper peripheries of the rolls 13, 14 and is precisely centeredbetween such rolls. This insures that both sides of the strip loop willincrease and decrease in length at the same rate as the loop increasesand decreases in size to preclude the application of a greater tensionon one side of the loop than on the other during a change in loop size.It is also an important feature of the invention that roll 19 issupported for movement by pivoted link means to provide for minimumfrictional resistance to such movement to thus increase the sensitivityof the present inventions strip tensioning function.

In order to provide the desirable features of constraining roll 19 torectilinear movement while supporting it for minimum frictionalresistance to such movement, roll 19 is supported by means known as theWatt Straight Line Movement. As best seen in FIGURES 2 and 4, such meanspresently comprises a first link means having one end pivoted to rollstand 15 and having its other end providing spaced leg portions forreceiving the roll 19 therebetween and pivotally secured to such roll bymeans to be disclosed. Second link means 21 is pivoted to roll stand 16at 22 and provides spaced leg portions for receiving roll 19therebetween. The means for connecting roll 19 to the link means 20, 21comprises short links 23 disposed at opposite ends of the roll 19 andhaving their intermediate portions rotatably connected to respectiveroll ends and having their end portions pivotally connected torespective adjoining ends of the link means 20, 21.

With the link mechanism thus far described, it will be understood thatas the link means 20 and 21 simultaneously swing in respective arcsabout their pivots thus bodily shifting roll 19, the latter will,nevertheless, move in a straight line because of the compensating effectof links 23 which tilt about the axis of roll 19 during such link meansmovement.

Since the weight of roll 19 and of the links 20, 21 and 22 may be sogreat that too much tension would be applied by such roll riding in theloop of material, means are provided to reduce the effective weight ofthe roll and the links. At the present time, this is done in thefollowing manner. Second link means 21 extends beyond pivot 22 andprovides in spaced relation with pivot 22 and on the opposite sidethereof from roll 19, a strut 24 which extends between the spaced legsof this link means. Pivotally secured to the central portion of strut 24is a depending rod 25 having a transversely extending flange 26 at itslower end (see also FIGURE 3). In order to reduce the effective weightof roll 19, it is only necessary to support on the rod flange 26a Weight27 suflicient to counterbalance, to the requisite degree, the weight ofroll 19. Similarly, if roll 19 does not have sutficient weight toprovide the requisite tension in the strip, weight may be added to theroll by placing weights upon a rod (FIGURE 2) depending from andpivotable with respect to the axis of roll 19.

Still referring to FIGURES 2 and 3, one end of strut 24 has a chain 28depending therefrom. The lower end of chain 28 is secured to a reactor29 which. controls the speed of drive means 18 to which the reactor isconnected by means of suitable electric wiring 129. Briefly, if the roll19 moves downwardly from the full line position shown in FIGURE 2, chain28 will cause elevation of a portion of the reactor to effect anincrease in the speed of the drive means 18. Conversely, if the roll 19moves upwardly from the full line position shown, chain 28 will permitthe reactor portion to be lowered to reduce the speed of the drive means13. With the speed of drive means 18 thus controlled, roll 19 will tendto remain positioned as seen in full lines during operation of theapparatus in tensioning the moving strip.

With the construction thus far described, operation will be as follows:Assuming that the strip is passed over the various rolls as seen inFIGURES 1 and 2 and is moving longitudinally in the direction of thearrows, assuming that the drive means 18 is rotating the rolls 14, 17 ata rate to withdraw the strip from the oven at the same rate at which itis fed into the oven by the pinch rolls 12, and further assuming thatcounterweight 27 is such that roll 19 applies the requisite tension tothe loop in the strip, it will be understood that the present apparatuswill maintain the strip portion within the oven under a predeterminedtension. If now, the pinch rolls 12 should, for any reason, begin tofeed strip to the oven at a slower rate, rolls 14, 17 which are stilloperating at the rate earlier mentioned, would tend to increase thetension on the strip portion intermediate the pinch rolls 12 and therolls 14, 17. However, if this occurs, the loop in the strip willdecrease in size as roll 19 moves upwardly to prevent an increase intension in the strip until such roll assumes, for example, the phantomposi tion indicated at A. This elevation of the roll 19 will effect areduction of speed of the drive means 18 to thus bring the operationalrate of the rolls 14, 17 into balance with that of the pinch rolls 12.

Conversely, should the pinch rolls 12 begin to operate at a higherspeed, the tension upon the strip would tend to decrease. This wouldcause the loop to increase in size as the roll 19 moves downwardly toprevent a decrease in the tension on the strip. As the roll 19 movesdownwardly from its full line position, it will cause an increase inspeed of the drive means 18 to thus once again bring the operationalrate of the rolls 14, 17 into balance with that of the pinch rolls.

From the foregoing, it will be understood that the loop in the strip inwhich roll 19 rides will increase in size to prevent a decrease in striptension and will decrease in size to prevent an increase in striptension. Additionally, by virtue of the speed regulation of the drivemeans 18, in accordance with the position of the roll 19 and thus inaccordance with the size of the loop, the operational rate of the rolls14, 17 will be maintained in balance with that of the pinch rolls 12.

Referring to FIGURES 5 and 6 wherein the rolls 13, 14 and 19 arediagrammatically shown in engagement with the strip, FIGURE 5illustrates the rolls in generally the same position in which they areseen in FIGURE 2 while FIGURE 6 illustrates the roll 19 in a positionelevated from that seen in FIGURE 5. With a given effective weight ofroll 19 and with the roll positioned as seen in FIGURE 5, the angularitywhich is indicated between the vertical path of movement of the roll 19and a side of the loop in the strip will result in a given tension beingapplied by the roll to the strip. Now, however, if roll 19 is elevatedto the position seen in FIGURE 6, the angularity above mentioned will begreatly increased, as illustrated, thus resulting in a greater tensionbeing applied to the strip by the roll even though the effective weightof the latter has not been changed. Conversely, if roll 19 is lowered,the above mentioned angularity decreases and thus the strip will betensioned a lesser amount even though the weight of the roll remainsconstant.

In order to eliminate, or at least reduce, the variation in tension inthe strip caused by the above described change in angularity whichresults from vertical movement of roll 19, the following construction isemployed: As seen in FIGURE 2 and with roll 19 positioned in its normal,full line position shown, it will be noted that strut 24, to which rodis secured, is positioned above a horizontal plane Z which passesthrough link means pivot 22. Accordingly, as roll 19 moves upwardly fromthe full line position shown, strut 24 will swing in an arcuate pathdownwardly toward plane Z. This arcuate movement of the strut causes aprogressive increase in effective length of the lever arm supporting thecounterweight 27 until such time as the axis of the strut coincides withthe plane Z.

With the foregoing in mind, assume that the roll 19 has moved upwardlyfrom the full line position seen in FIGURE 2 to the phantom position A.In so moving, the angularity disclosed with respect to FIGURES 5 and 6,will increase, thus tending to subject the strip to a greater tension;however, in moving upwardly, roll 19 has caused strut 24 to movedownwardly toward the plane Z thus increasing the effective length ofthe lever arm supporting the counterweight 27 and therefore increasingthe latters effectiveness in counteracting the Weight of the roll 19.With an increase in effectiveness of the counterweight, the effectiveweight of the roll 19 will be decreased thus tending to decrease thestrip tension. It will be clear that in order to prevent an increase intension on the strip When roll 19 moves upwardly, it is only necessaryto so arrange the parts that the decrease in effective weight of roll 19caused by an increase in the effective length of the lever armsupporting the counterweight will balance the tendency of the roll toincrease strip tension as the roll moves upwardly. It will also be clearthat as roll 19 moves downwardly from its full line position, theangularity mentioned in with respect to FIG- URES 5 and 6 will decrease,thus tending to decrease the tension on the strip. However, suchmovement of roll 19 will cause strut 24 to move upwardly to decrease theeffective length of the lever arm supporting the counterweight andtherefore increase the effective weight of the roll to counteract thetendency of the latter to tension the strip a lesser amount.

As hereinbefore mentioned, roll 1-9 need not be used when relativelyheavy strip is being handled; accordingly, when such is the case, thisroll may be elevated to the position seen in phantom lines at B inFIGURE 2 and supported in this position by any suitable latch or thelike to thus eliminate the loop in the strip and permit the strip topass directly from roll 13 to roll 14.

In view of the foregoing, it will be apparent to those skilled in theart that I have accomplished at least the principal object of myinvention and it will also be apparent to those skilled in the art thatthe embodiment herein described may be variously changed and modified,without departing from the spirit of the invention, and that theinvention is capable of uses and has advantages not herein specificallydescribed, hence it will be appreciated that the herein disclosedembodiment is illustrative only, and that my invention is not limitedthereto.

I claim:

1. Apparatus for maintaining a predetermined tension on longitudinallymoving tenuous material, comprising a plurality of rotatably mountedrolls over which the material passes in the form of a loop and one ofsaid rolls riding in said loop and being movable transversely of itsaxis in a rectilinear path as said loop changes in size and exerting aforce tending to enlarge said loop and thus tension said material, and aplurality of pivotally interconnected link members connected to said oneroll and constraining the latter to movement along said rectilinear pathwith minimum frictional resistance.

2.. Apparatus for maintaining a predetermined tension on longitudinallymoving tenuous material, comprising a pair of rotatably mounted rolls inspaced-apart, side by side relation over which the material passes andbetween which such material assumes a loop formation, a third rollriding in the loop of said material and movable transversely of its axisin a rectilinear path toward and away from said roll pair as said loopchanges in size and exerting a force tending to enlarge said loop andthus tension said material, and a plurality of pivotally interconnectedlink members connected to said third roll and constraining the latter tomovement along said rectilinear path with minimum frictional resistance.

3. Apparatus for maintaining a predetermined tension on longitudinallymoving tenuous material, comprising a pair of rotatably mounted rolls inspaced-apart side by side relation over which the material passes andbetween which such material assumes a loop formation, a third rolldisposed in the loop of said material and movable transversely of itsaxis as said loop changes in size and exerting a force tending toenlarge said loop and thus tension said material, and a plurality ofpivotally interconnected link members connected to said third roll andconstraining the latter to movement with minimum frictional resistancein a rectilinear path perpendicular to a plane passing through the axesof said roll pair.

4. Apparatus for maintaining a predetermined tension on longitudinallymoving tenuous material, comprising a pair of rotatably mounted rolls inspaced-apart side by side relation over which the material passes andbetween which such material assumes a loop formation, a third rolldisposed in the loop of said material and movable transversely of itsaxis as said loop change in size and exerting a force tending to enlargesaid loop and thus tension said material, and a plurality of pivotallyinterconnected link members connected to said third roll andconstraining the latter to movement with minimum frictional resistancein a rectilinear path perpendicular to a plane tangent to theperipheries of the roll pair.

5. Apparatus for maintaining a predetermined tension on longitudinallymoving tenuous material, comprising a pair of rotatably mounted rolls inspaced-apart, side by side relation over which the material passes andbetween which such material assumes a loop formation, a pair of linkmembers adjacent said rolls swingable about respective transverselyspaced pivots and each link member extending toward the pivot of theother to dispose portions of respective link members in spaced-apartadjoining relation intermediate said pivots, a third link memberpivotally connecting said portions of respective link members of saidpair, and a roll rotatably carried by said third link memberintermediate its pivotal connections with respective link members ofsaid pair, said roll riding in the loop of said material and exerting aforce tending to enlarge said loop and thus tension said material andsaid roll being constrained by said link members to movement withminimum frictional resistance transversely of its axis in a rectilinearpath toward and away from said roll pair as said loop changes in size.

6. Apparatus for maintaining a predetermined tension on longitudinallymoving tenuous material, comprising a plurality of rotatably mountedrolls over which the material passes in the form of a loop and one ofsaid rolls riding in said loop and being movable transversely of itsaxis in a rectilinear path as said loop changes in size, first andsecond means operable to respectively feed material to said loop and towithdraw material therefrom at predetermined rates, a plurality ofpivotally interconnected link members connected to said one roll andconstraining the latter to movement along said rectilinear path and withminimum frictional resistance, and means responsive to the position ofsaid one roll along said rectilinear path for varying the relativeoperating rates of said first and second means in accordance with theposition of said one roll.

7. The construction of claim 1 wherein said one roll is shiftable awayfrom engagement with the material when tensioning of the latter is notrequired.

8. The construction of claim 5 wherein said link members are duplicatedat respective ends of said roll.

References Cited in the file of this patent UNITED STATES PATENTSRobinson- Feb. 7, 1893 Gates Nov. 29, 1932 Bedell June 26, 1934 ClineJuly 2, 1935 Cohn et a1 Sept. 5, 1939 Stone et a1. Sept. 25, 1951

